The subject of the present invention is a device for feeding an extrusion head for plastic material.
Devices of this kind, already known, are used especially for fabricating by extrusion elongated products of plastic material presenting a colored surface layer.
It is usual to use two method for that:
1. Master-batches of colors are added to the mass of plastic material,
2. An additional extruder is used, which deposits a colored surface skin around the extruded shape.
The second method has the advantage of saving on the coloring agents since only a thin layer of the extruded product is colored.
The object of the present invention is to improve the feed devices already known, in order to apply the second method described above by achieving an instantaneous change of color without waste of material.
To this end, the device according to the invention is characterized in that is comprises a main extruder connected to a main die and a feed means associated with the main die and capable of being selectively controlled so as to cover the exit flow of the main die with a surface layer formed of successive segments, the appearance of which differs.